The present disclosure generally relates to heat exchangers, and more particularly, to a heat exchanger having anti-icing provisions.
Aircraft use cooling systems to manage thermal loads resulting from equipment operation. These cooling systems frequently include heat exchangers having separate hot and cold flowpaths. Heat from fluid in the hot flowpath is transferred to fluid in the cold flowpath, thereby cooling the fluid in the hot flowpath and heating the fluid in the cold flowpath. For example, air from compartments having equipment giving off heat can be directed through the hot flowpath and air from a cooling turbine of an air cycle machine (i.e., a refrigeration unit) can be directed through the cold flowpath. The heat exchanger transfers thermal energy from the hot flowpath air to the cold flowpath air, thereby cooling the air from the equipment compartment. The cooled air is returned to the equipment compartment, cooling the equipment to ensure proper performance.
Air entering conventional heat exchangers from cooling turbines must be maintained at a temperature above a freezing temperature of water to prevent ice from accumulating on surfaces of the cold flowpath in the heat exchanger. If the temperature of the air entering the heat exchanger is below the freezing temperature of water, multiple layers of ice can accumulate on surfaces along the cold flowpath. These layers of ice impair the heat exchanger by increasing power required to pump air through the heat exchanger and insufficiently cooling fluid in the hot flowpath. However, if colder air could be used in the heat exchanger without ice accumulating, then the air cycle machine efficiency could be increased and the heat exchanger size and weight could be reduced. Thus, there is a need for a heat exchanger that reduces the potential for ice accumulation.